# How to Build a Custom GPT (No Code)

> Custom GPT creation now needs a Business, Enterprise or Edu workspace. Use the Configure tab for instructions, up to 20 knowledge files, and actions.

- Canonical: https://guides-ai.pages.dev/guides/build-a-custom-gpt/
- Plate 07.03 · Topic: ChatGPT (https://guides-ai.pages.dev/topics/chatgpt/)
- Published: 21 Aug 2026 · Updated: 06 Sept 2026 · 3 min read
- Source site: guides-ai — https://guides-ai.pages.dev/

A custom GPT is ChatGPT pre-loaded with your instructions, your files and a chosen set of
tools. Read this before you start: **new GPT creation and publishing are no longer available
on personal ChatGPT accounts.** You need a Business, Enterprise or Edu workspace, and your
workspace settings have to permit it. On a personal Plus or Pro account, use
[ChatGPT Projects](/guides/chatgpt-projects/) instead — same instructions-and-files idea,
without sharing or actions.

## 1. Open the builder, then switch to Configure

The builder offers a conversational route where you describe what you want, and a
configuration view where you edit the fields directly. Use **Configure**: it is the only place
you see exactly what the GPT will be told.

## 2. Write instructions that constrain the answer

Instructions are a [system prompt](/glossary/#system-prompt) with a form around it. Vague
instructions get ignored; rules with a shape get followed.

```text
You are a support assistant for [product].
- Answer ONLY from the uploaded docs. If the answer isn't there, say so and point to support.
- Keep answers under 120 words, then offer to go deeper.
- Never invent prices, dates, or policy.
```

What it does: fixes the role, forbids answering outside the knowledge files, caps the length,
and names the failure mode you most want avoided.

OpenAI's own guidance: when the GPT must apply specific classifications, include short examples
of acceptable and unacceptable output, and use headings and lists so priorities stay visible.

## 3. Add knowledge and capabilities

**Knowledge** takes up to **20 files, each up to 512 MB** — reference material the GPT draws
from during a conversation, as opposed to instructions, which say how to behave.
**Capabilities** are the toggles for tools such as web search and image generation. Actions let
the GPT call an external API you describe with an OpenAPI schema.

## Verify it worked

Save, then open a fresh chat with the GPT and ask something deliberately outside the uploaded
files. A correctly instructed GPT says it doesn't know and points at support; one that
confidently invents an answer needs a firmer instruction, not more files. That failure is
ordinary [hallucination](/glossary/#hallucination) — grounding it in the knowledge files is the
fix. Next: [write a system prompt that steers the model](/guides/write-a-system-prompt/).

Source: [Creating and editing GPTs](https://help.openai.com/en/articles/8554397-creating-and-editing-gpts).